By developing a long-term supranational perspective, this ambitious, multi-faceted work provides a new understanding of 'totalitarianism', the troubling common element linking Soviet communism, Italian fascism and German Nazism. The book's original analysis of antecedent ideas on the subject sheds light on the common origins and practices of the regimes. Through this fresh appreciation of their initial frame of mind, Roberts demonstrates how the three political experiments yielded unprecedented collective mobilization but also a characteristic combination of radicalization, myth-making, and failure. Providing deep historical analysis, the book proves that 'totalitarianism' best characterizes the common features in the originating aspirations, the mode of action and even the outcomes of Soviet communism, Italian fascism and German Nazism. By enhancing our knowledge of what 'totalitarianism' was and where it came from, Roberts affords important lessons about the ongoing challenges, possibilities, and dangers of the modern political experiment.